UN aid agencies say it is very difficult to meet the needs of millions of flood victims in Pakistan because of the huge scale of the disaster. The agencies report 14 million people are affected and nearly half that number is in direct need of humanitarian assistance for their survival.

UN and international aid agencies say Pakistan's flooding is testing both the government's and their ability to respond to the country's emergency.

They report thousands of villages and towns in low-lying areas have not seen flooding on this scale in generations.

Pakistan's Federal Flood Commission reports more than 300,000 homes have been destroyed or damaged, more than 14,000 cattle have perished and 2.6 million acres of cropland are under water. So far, about 1600 deaths have been confirmed. But, this figure is expected to rise.

The UN refugee agency has been caring for millions of Afghan refugees in Pakistan for years. It's main relief work is in the north where flooding is the most severe.

Given the enormity of the disaster, UNHCR spokesman, Andrej Mahecic, says the UNHCR now is working equally for all affected communities, both Pakistanis and Afghans.

"Currently some routes are blocked, and in several places we are contending with difficult security conditions," Mahecic said. "When we deliver tents people may also lack dry land where they can put up these tents. Among those caught in floods, there are many tenant farmers and also Afghan refugees living out on the inundated flood plains-indeed of the 1.7 million registered Afghan refugees in Pakistan, 1.4 million reside in the worst hit areas. Many people are now without shelter and have lost their food, livestock and all their possessions."

Mahecic say the UNHCR is working in coordination with the government, UN agencies and charities on the ground to provide the needed food, water, shelter, and medicine.

He says his agency's stockpiles of relief items in Balochistan Province are nearly exhausted. And, in parts of the Swat Valley, he says thousands of people in need of aid remain inaccessible.

The World Food Program has been airlifting supplies to people trapped in villages cut off by road. But, because of bad weather conditions, its helicopters were grounded for three days. As a consequence some 600,000 people in the Swat Valley were cut off from assistance.

"So far, we now have been able to reach nearly 340,000 people with a one month food ration in the worst parts of the affected area," Casella said. "But, the situation still remains considerably difficult. We are now targeting…up to six million people with food assistance as a result of the floods."

Casella says some of the people will need assistance for only a short period of time. But, she says WFP expects about two million will likely need help for at least three months.

On Wednesday, the U.N. Secretary-General will be appealing for hundreds of millions of dollars for U.N. humanitarian operations in Pakistan. The World Food Program says it will request $150 million as part of that appeal.